Which Colour space?
Most customers are using monitors with standard gamuts, so sRGB is probably best for most work.

If you have a wide-gamut monitor you should consider using Adobe (1998) colour space to get the most from our printer. We can accept Adobe (1998) as our printer can print this gamut. If you have a standard gamut monitor (such as an i-Mac or most off the shelf monitors) you do run the risk that we will print colours in your print that were in your file but you could not see on your monitor due to your display’s restricted colour gamut.